The invention concerns a device to lock the blades of a turbofan and to fasten the front cowl of a turbojet engine, with the blades being retained in the axial grooves of the rotor.
In the turbofans of conventional turbojet engines, the blades are locked in axial grooves of the rotor in a manner to be immobilized both radially and axially. Generally, a wedge is slid between the root of the blade and the bottom of the groove, with the wedge being of a size so that the root is urged against the upper flanks of the groove. The axial displacement of the blade is prevented by a bolt placed in radial grooves provided in an extension of the rim in front of the rotor disk and in a part of the blade root corresponding to said extension.
A device of this type is described in French Pat. No. 2,345,605, wherein the wedge prevents the radial movement of the bolt, with the axial movement of the wedge being prevented by a stop consisting of a lip provided in the front cowl fastened to a flange of the rotor and by a projection provided on the wedge itself. The replacement of a blade thus requires the removal of the cowl, the withdrawal of the wedge and the bolt, after which the blade may be extracted from the groove by means of axial sliding. The use of the locking device is relatively simple, but it requires at least in the downstream direction, a flange mounted on the disk to support the cowl and blade roots of a length at least equal to the axial extensions of the rim, generally called "teeth" for the housing of the bolt.
The flange and the blade roots represent a non-negligible weight, which further increases the overhang of the rotor. Furthermore, the machining of the roots adds to the costs of production.